1. Field of the Invention
The present invention relates to a display apparatus and an imaging system using the same.
2. Description of the Related Art
Recently, developments of organic electroluminescence (organic EL) have been actively pursued.
For example, Japanese Patent Application Laid-Open No. 2003-272857 discloses a white organic EL device including a blue (B) light emitting layer and a yellow (Y) or red (R) light emitting layer that are stacked.
In addition, there is known a display apparatus that can emit color light, which includes materials emitting red, green (G) and blue colors and an organic layer formed and stacked on a substrate so as to form sub-pixels arranged in the form of matrix.
There is also known a color matrix display apparatus having a similar color configuration. This display apparatus includes a material emitting white (W) color and an organic layer formed and stacked on a substrate so as to form a matrix, on which color filters of R, G and B are stacked.
Further, there is also known a matrix display apparatus including W sub-pixels without a color filter in addition to the above-mentioned R, G and B sub-pixels with the color filter, so the R, G, B, and W sub-pixels perform color display. For example, U.S. Pat. No. 6,570,584 discloses a display apparatus including sub-pixels of colors more than R, G and B.
U.S. Pat. No. 6,570,584 discloses a method for driving such a device, in which light emissions of an R light emitting device, a G light emitting device, a B light emitting device and a W light emitting device are mixed based on a calculation so that a desired color can be generated.
On the other hand, Japanese Patent Application Laid-Open No. 2006-163068 describes that the chromaticity of white obtained by a light emitting material is actually not a target chromaticity of white in many cases, so it is necessary to add light emission of an RGB unit pixel for color matching to a white light emission of a unit pixel for a white display. Japanese Patent Application Laid-Open No. 2006-163068 also discloses a signal processing way, in which an RGB input signal is mixed when the light emission chromaticity of the W pixel is different from the target chromaticity of white.
It may be considered from the above-mentioned descriptions that it is not necessary to mix the light emissions of R+G+B sub-pixel group for color matching to the light emission of the W sub-pixel for white display when the light emission chromaticity of the W sub-pixel is set to the target chromaticity of white so as to be adapted to the light emission chromaticity of the R+G+B sub-pixel group.
However, in case of light emission without using interference (PL light emission or the like), metamerism occurs as it is as the light emission color. Even when the light emission colors are mixed, the same color appears. For example, there are prepared a “light emission in which light emission of a light emitting device used as a sub-pixel is mixed at a certain rate” and a “light emission from a sub-pixel of metamerism although the light emission has a spectrum shape different from that of a mixed spectrum of the light emission in which light emission of a light emitting device used as a sub-pixel is mixed at a certain rate.”
In the following descriptions, the “light emission in which light emission of a light emitting device used as a sub-pixel is mixed at a certain rate” is referred to as “mixed light of sub-pixel group” in abbreviation. The “light emission from a sub-pixel of metamerism although the light emission has a spectrum shape different from that of a mixed spectrum of the light emission in which light emission of a light emitting device used as a sub-pixel is mixed at a certain rate” is referred to as “light emission from a sub-pixel of metamerism” in abbreviation.
In addition, a combination of plural light emissions of sub-pixels having different light emission colors is expressed by using “+”. For example, a combination of light emissions of an R sub-pixel, a G sub-pixel, and a B sub-pixel is referred to as “light emissions of R+G+B sub-pixel group.”
Note that, the sub-pixel means a unit of the light emitting device that can control on and off of light emission or gradation of the same. The pixel is a set of sub-pixels and means a minimum unit of a color display.
When those light emissions are mixed without interference, each light emission of the “mixed light of sub-pixel group” and the “light emission from a sub-pixel of metamerism” has the same CIE chromaticity coordinates as the mixed light thereof (hereinafter referred to as “chromaticity coordinates” simply).
However, in case of a display apparatus using interference between light emission from a light emitting device and reflection light from a reflector plate, the “mixed light of sub-pixels” and the “light emission from a sub-pixel of metamerism” have different chromaticity coordinates.
This is because that intensity of light due to interference has a characteristic according to a wavelength in a display apparatus including an interference structure under a certain condition. Therefore, in case of the above-mentioned light emissions in which different spectra of light are emitted, the spectrum after the interference is modulated so that chromaticity coordinates calculated from an integral value of the spectrum is also changed.
In the case where a W sub-pixel having different spectrum in metamerism is provided as fill light to the B+Y sub-pixel group, for example, the spectrum after the interference is modulated so that chromaticity coordinates calculated from an integral value of the spectrum is also changed.
In addition, since the spectra of both light emissions are different from each other, chromaticity after the interference is changed when a mixing ratio between the light emissions of R+G+B sub-pixel group and the light emission of W sub-pixel is changed.
In addition, when a view angle is tilted from a normal direction of a display surface so that an interference condition is changed, the chromaticity of light emissions of the B+Y sub-pixel group and the chromaticity of light emission of the W sub-pixel are changed so as to be different from each other.
In the above-mentioned Japanese Patent Application Laid-Open No. 2006-163068, light of R and/or G and/or B is emitted for color matching in case of the R+G+B sub-pixel group+the W sub-pixel. According to this control, the chromaticity can be matched with each other. However, since the spectra of both light emissions are different from each other, chromaticity after the interference is changed when the mixing ratio between the light emissions of the R+G+B sub-pixel group and the light emission of the W sub-pixel is changed.
In addition, when the view angle is tilted from the normal direction of the display surface so that the interference condition is changed, the chromaticity of light emissions of the R+G+B sub-pixel group and the chromaticity of light emission of the W sub-pixel are changed so as to be different from each other in the same manner as the above-mentioned example.
As a result, even when the chromaticity coordinates of the “mixed light of sub-pixel group” and the chromaticity coordinates of the “light emission from a sub-pixel of metamerism” are combined to form the metamerism, chromaticity coordinates of white obtained from the display surface of the display apparatus after the interference may be deviated from an expected value when the spectra are shifted.
Note that, also in the color filter type R, G, B and W display apparatus described as a background art, the R, G and B color filter arranged on the white color matrix substrate may narrow individual wavelength ranges. Therefore, even when the light emissions of the R, G and B light emitting devices are mixed, the spectrum of the mixed light does not match the spectrum of the light emission of the W sub-pixel without the color filter.